The present invention relates to an improvement in the use of lead frames of the type employed as a component of ceramic dual in line packages, commonly referred to as cer-dips in connection with integrated circuit technology. The invention more particularly has reference to locating eye point markings on the terminals of the lead frames.
Cer-dip lead frames to which ceramic bases of chips are secured are well known in the semiconductor field and have been used in many different forms in the past in ceramic packaging technology. The lead frames are generally made from a very thin strip of aluminum/nickel/iron alloy and formed into the lead frame shape by a series of stamping operations.
As an essential part of the wire bonding operational step in the manufacture of the packages, which step is performed automatically by a computer driven machine, it is necessary to determine the exact location of the outer end of each terminal lead of the frame in order to position the frame relative to the welding elements of the bonding machine. This is done by the bonding machine making an optical camera examination of two diametrically oppositely arranged leads and using this determination to mathematically calculate the exact locations of all of the ends of the remaining terminal leads.
Since the location of the ends of the leads is done optically, it is dependent on the ability of the viewing instrumentation to accurately and quickly detect the two opposite ends of the selected terminals
Because, however, of certain more or less inherent conditions surrounding the viewing, the locating step can not be quickly and accurately performed. This is due, in part, to the fact that the various components that have been attached to the frame before the frame is advanced to the wire bonding operation, for example the ceramic base, provide a very poor background for optical camera detection of the terminals of the frame, along with the fact that the frame and particularly the terminal ends themselves create a poor backdrop for camera viewing.